Microwave chip carrier

Abstract

An all-metal microwave chip carrier is provided with subminiature ceramic feedthroughs, each configured to function as a coaxial cable having a predetermined impedance. In one embodiment, the feedthroughs are formed by providing ceramic tubing metallized inside and out in which the ends are cut away to provide half-cylindrical bonding pads. In order to permit bonding directly to the feedthrough, a flat wire lead is soldered to the channel in the ceramic tube, with the ends of the flat wire extending onto the flat portions of the half-cylindrical portions of the feedthrough. In one embodiment, the chip carrier includes a base, ring, and stepped lid, all of Kovar or other suitable material, with the lid being weldable to the ring rather than being brazed or soldered.

What is claimed is: 
     
       1. Apparatus for housing a microwave device comprising: an all-metal housing including a base, an intermediate ring mounted to said base and in electrical contact therewith, and a lid adapted to be electrically and hermetically sealed to said ring, said ring having a side wall having a bore therethrough, and   a subminiature feedthrough inserted in said bore, said feedthrough having a coaxial configuration including a ceramic tube having an interior and exterior metal coating, and an inner conductor positioned through said tube along the longitudinal axis thereof and being in electrical contact with the interior metal coating of said tube, said tube including an at least partially cut-away portion to one side of said sidewall to expose a portion of said conductor.   
     
     
       2. The apparatus of claim 1 wherein said ring and lid are made of a material which permits welding said lid to said ring. 
     
     
       3. The apparatus of claim 2 wherein said lid and ring are an iron-nickel-cobalt alloy. 
     
     
       4. The apparatus of claim 1 wherein said conductor includes a flat wire, and wherein said cut-away portion is flat and lies in a plane parallel to the width of said flat wire, thereby to provide a contact pad. 
     
     
       5. The apparatus of claim 4 wherein said cut-away portion is half-cylndrical. 
     
     
       6. The apparatus of claim 4 wherein the space between said flat wire and said interior metallization is filled with electrically conductive material. 
     
     
       7. The apparatus of claim 6 wherein said electrically conductive material is solder. 
     
     
       8. The apparatus of claim 1 wherein said bore is open at the bottom thereof and wherein the exterior coating of said tube is in intimate contact with said base through the open bottom of said bore. 
     
     
       9. The apparatus of claim 1 wherein said feedthrough is no more than 50 mils in diameter. 
     
     
       10. A subminiature feedthrough for use in the packaging of microwave components comprising: a length of dielectric tubing metallization interiorally and exteriorally, an end of said tubing being cut away to provide a flat portion at an end of the tube adjacent the tube channel, and   a flat wire in said channel and extending to the vicinity of said flat portion such that the wide portion of said wire lies in a plane parallel to that of said flat portion, thereby to provide an accessible contact pad at an end of said tubing.   
     
     
       11. The feedthrough of claim 10 wherein the dimensions and dielectric constant of said tube are chosen to provide the resulting coaxial structure with a predetermined electrical impedance. 
     
     
       12. The feedthrough of claim 10 wherein the edges of said flat wire contact the interior metallization of said tubing. 
     
     
       13. The feedthrough of claim 10 wherein said tubing is made of ceramic material. 
     
     
       14. The feedthrough of claim 10 wherein said tubing is made from glass. 
     
     
       15. The feedthrough of claim 10 wherein the outer diameter thereof is less than 50 mils. 
     
     
       16. The feedthrough of claim 10 wherein the space between said flat wire and said interior metallization is filled with electrically conductive material. 
     
     
       17. The feedthrough of claim 16 wherein said electrically conductive material is solder. 
     
     
       18. A method of forming a subminiature electrical feedthrough having a coaxial structure comprising the steps of: metallizing an electrically nonconductive tube on the interior and exterior walls thereof;   cutting away at least one end portion of the metallized tube to provide a half-cylindrical portion; and   passing a wire through the interior channel of the metallized tube, such that the wire makes electrical contact with the interior metallized wall of the tube and such that a portion of the wire extends to the half-cylindrical portion.   
     
     
       19. The method of claim 18 wherein said wire is flat. 
     
     
       20. The method of claim 18 wherein said wire is soldered to said interior metallized wall.